Markuelia is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 worm-like bilaterian animal

Bilateria

The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back...

s allied to Ecdysozoa and known from strata of Lower Cambrian to Lower Ordovician age containing five species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

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An advanced X-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 imaging technique called called X-ray tomographic microscopy has been applied to splendidly preserved, uncrushed Markuelia fossils found in Hunan

Hunan

' is a province of South-Central China, located to the south of the middle reaches of the Yangtze River and south of Lake Dongting...

 province in southern China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 and in eastern Siberia

Siberia

Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

. When details in features smaller than one micrometre

Micrometre

A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

 across can be observed, these fossils are seen to represent many developmental stages, from the first cell divisions to the time of hatching; therefore they offer a unique opportunity to study the development of Lower Cambrian animals.

The features observed indicate that the genus had a mouth surrounded by a ring of teeth (suggesting a carnivorous diet), an alimentary canal, and an anus

Anus

The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...

 - being the earliest known examples of this set of features.

However the characters preserved are inconclusive regarding the genus' taxonomic affinity; it can at best be placed in the scalidophoran total group, since it is currently impossible to ally it with the Priapulids or other scalidophora

Scalidophora

Scalidophora is a group of marine pseudocoelomate invertebrates, consisting of the three phyla Kinorhyncha, Priapulida, and Loricifera. The members of the group share a number of characteristics, including introvert larvae and moulting of the cuticle...

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